This invention provides a tubing hanger assembly for use in a tubing bead of a production well. The tubing hanger assembly provides for passage of production fluids from the production tubing mounted therebelow, through the tubing hanger assembly, while also providing isolation of the production tubing from an electrical power cable to pass through the tubing hanger assembly.
Within a wellhead, the production string forms the primary conduit through which production fluids (liquids, gases, or any fluid produced from a wellbore) are produced to the surface. The production string is typically assembled with production tubing and completion components in a configuration that suits the wellbore conditions and the production method. An important function of the production string is to protect the primary wellbore tubulars, including the casing and liner, from corrosion or erosion by the production fluid. The production tubing is secured and supported in the wellhead by a tubing hanger which is a common component positioned inside a tubing head. It is common to use electric motor driven downhole pumps to augment the downhole pressure, with the electrical power cable routed from the downhole pump motor to the wellhead.
Canadian Patent Application No. 2,327,987, laid open on Jun. 8, 2001, to Robbins and Myers Energy Systems, L. P., discloses a wellhead for use in a subterranean well, including a tubing hanger with an electric power cable pack-off port that permits positioning of an electric submergible pump power cable through the port in the tubing hanger. The wellhead permits installation of packing and compression rings around the power cable to create a vapor-tight pressure seal around the outer cable jacket. The seal is stated to be rated at pressures of at least 750 psia. However, higher pressures might be encountered in a wellbore. Furthermore, this device does not enable testing of the integrity of the seals or protect the cable from a high pressure test of the production side.
U.S. Pat. No. 4,600,054, issued Jul. 15, 1986 to Miller et al., discloses a segmented tubing hanger to support tubing strings with the feature of allowing the sealed passage of electrical cable through the tubing hanger. However, the device requires that the tubing hanger section be moved to permit access to the seals for pressure testing, and does not enable re-energizing of the packing. An isolation system whereby the production tubing is kept separate from the electrical power cable is also lacking.
Presently, the prior art is thus lacking in that it is important that the tubing hanger incorporates certain features such as a sealing system to ensure that the production tubing is isolated from the electrical power cable. The tubing hanger should be designed such that pressure testing of the sealing system is easily accessible. Furthermore, protection of the electrical power cable from pressure testing in the tubing is desirable.
This invention provides a tubing hanger system which permits isolation and protection of the production tubing from the electrical power cable. Preferably, the system enables pressure testing of the integrity of both the production and cable seals, without requiring disassembly of the tubing hanger or any other components or damaging the electrical power cable, in advance of high pressure operations. Further, the tubing hanger system protects the cable from higher pressures encountered in the production tubing. The invention thus provides ease of pressure testing of the sealing means, and provides isolation of the electrical power cable from flange pressure testing.
Broadly stated, the invention provides a tubing hanger assembly for use in a tubing head of a production well, and which provides for passage of production fluids from the production tubing mounted therebelow, through a central bore in the tubing head and through the tubing hanger assembly, while also providing isolation of the production tubing from an electrical power cable which passes through the tubing hanger assembly. The tubing hanger assembly comprises:
a generally cylindrical tubing hanger member adapted to seat in a landing seat in the tubing head, and to seal against the central bore;
a tubing head adapter adapted to be fastened above the tubing head so as to enclose the tubing hanger member in a sealed relationship therebetween;
the tubing head adapter and the tubing hanger member together forming two aligned, parallel spaced ports extending therethrough to provide a tubing port, which connects to the production tubing and permits passage of production fluids, and a cable port through which the electrical power cable extends;
the tubing hanger member forming a seat in the cable port;
a cylindrical tubing seal-off nipple adapted to connect and seal the tubing port in each of the tubing head adapter and the tubing hanger member;
a cylindrical cable seal-off nipple adapted to seat against the seat in the cable port, and to connect and seal the cable port in each of the tubing head adapter and the tubing hanger member;
a first seal below the cable seal-off nipple for sealing between the electrical power cable and the cable port in the tubing hanger member;
a second seal above the cable seal-off nipple for sealing between the electrical power cable and the cable port in the tubing head adapter;
whereby, the tubing seal-off nipple and the cable seal-off nipple when sealed in the tubing and cable ports, provide isolation of the production tubing from the cable port and the electrical power cable held therein.